An aggregation of analog signals by means of adders is described for example in the textbook "Semiconductor circuit technology" by Tietze and Schenk, 8th. edition, 1986, pages 299 and 300 as well as 579 to 581.
The aggregation of digital signals from analog input signals with an intermediate analog-digital converter (ADC) via a digital signal processor (DSP), and a reanalogation of the processed signals by means of a digital-analog converter (DAC), particularly in the area of video signals, is described for example in EP 0 695 066 A2.
A linear aggregation of several band-limited time signals into a new composite signal takes place among other things in audio technology, where audio signals are superimposed by mixing the sounds from several different sources, or in video technology where video signals are combined into a new video signal by cross-fading the images from two different sources. The areas of application for sound mixing are for example in radio, in the disk recording industry and in the production of other sound carriers. Furthermore, sound mixing is required for audio conference circuits, i.e. for the aggregation of several sound signals from different sources in the area of telecommunications. A mixing of images by cross-fading several video signals is usual for example in television, in the production of video disks and video displays on other video carriers, video recorders, camcorders and such. Although no video mixing takes place in video conferences, windows are faded into a joint video for the different participants in the conference system.
With the method for mixing low frequency signals known from the DE 32 00 934 A1 cited in the beginning, which are present in the form of digital scanning samples, the pulses intended for the common terminal, which must be rendered jointly audible in the respective terminal, are aggregated by an analog adder and are transmitted within one time frame in the form of an aggregate pulse which controls the terminal during the entire time frame.
A disadvantage of the known methods is the relatively long calculation time for the aggregation of the individual signals by a digital computer, or by a hardware circuit of adding units. In addition there is considerable damping of the signals and thus a loss of information when converting from analog to digital signals and vice versa during the reanalogation of the added signals in the case of a digital aggregation.